<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script src="jquery-3.7.1.min.js"></script>
</head>
<body>
    <div style="color: red;">one div</div>
    <ul>
        <li>11</li>
        <li>22</li>
        <li>33</li>
        <li>44</li>
    </ul>
    <div>one div</div>
    <button>点击观察</button>
    <script>
        let aa = $("div").css("color");
        console.log(aa);
        $("div").css("color","green");

        $("ul").append("append被选元素的结尾");
        $("ul").prepend("prepend被选元素的开头");
        $("ul").after("after被选元素之后");
        $("ul").before("before被选元素之前");

        $("button").click(function(){
            $("div").remove();
            $("div").empty();
        })
    </script>

</body>
</html>